Verci, I can not answer intelligently on the "due regard" part for UAVs. Your guess is as good as mine. The issue of flying due regard/tactical with your transponder on is a discussion best saved for another thread.
That being said, when you call the UAV "it" responds. Obviously has a relay to the operator (a 14 year old PS3 wizzkid in Maine?) and even a telephone number so you can call him for a chat.